New developments, in particular in the field of security for the prevention of injuries, have made cutting hand tools more sophisticated, more complex to produce and therefore more expensive. Such cutting hand tools represent a true investment for companies and as a result, they should be made to last. While the sustainability of these tools is being constantly improved, the lifetime of a blade may not exceed a few days or even only hours in the context of intensive industrial use until its cutting edge becomes unsuitably dull. Moreover, the sharper the blade, the easier it can become damaged. Accordingly, blade replacement means have become standard features for many cutting hand tools on the market. Yet, if changing a blade is fairly straightforward on a regular cutting hand tool with a fixed blade, it is more challenging in the case of a blade slidably mounted into the housing.
In practice, blade replacement methods differ according to the position of the blade during the exchange: the blade may be replaced either in the rear position, when it is completely retracted into the housing, or in various front positions, when it partially protrudes out of the housing.
U.S. Pat. No. 8,375,588 and US 2013/0091712 show examples of cutting hand tools with a slidable and exchangeable blade, where the blade is replaced in its rear position. However, having to open the whole housing every time the blade needs changing is tedious. In addition, this exposes the inner components of the knife and may have several unwanted consequences. First, some component may fall out by inadvertence. Then, dirt, wood chips, sand, or grease may land thereon from the worker's hands or from the workplace environment, which would seriously compromise the proper functioning of the cutting hand tool, especially if it contains moving parts. Besides, no inner component can be anchored on any detachable part of the housing, for this part has to be able to move freely when opening the housing. So, all the inner components of such knives may end up being fixed to one region of the housing only.
More recent inventions relate to cutting hand tools where the blades can be replaced in the front position, thus avoiding the need of opening the complete housing for the replacement. However, the blade is never fully pushed out and its securing means remains concealed within the housing. So, the lack of a direct view of the way the blade interlocks with the securing means makes the replacement of the blade trickier. AU 2011201623 discloses a knife with a sliding blade which can be replaced in the front position, the blade being biased towards the rear position with a spring. So, in order to prevent the blade from sliding back into the housing during the replacement, it can be locked in the front position. This defeats the purpose of biasing it towards the rear position, which is meant to protect the blade automatically when the tool isn't being used. If it is possible to lock the blade in the unsheathed position, the worker will choose to do so and leave the blade permanently unsheathed for convenience. As a result, he is likely to get injured in a moment of inattention. Alternatively, AU 2011201624, U.S. Pat. No. 8,769,826 and US 2014/317936 disclose similar cutting hand tools whose blades cannot be locked into the front position but require the user to keep pushing on a slider during the replacement. However, this is tiring and prevents the user from using his two hands for replacing the blade, which makes the operation trickier.